Tammy Post's Iowa State Fair blue-ribbon recipe doesn't skimp on apples, which results in incredibly moist and indulgent bars.
Preheat oven to 350°. In a medium bowl, combine 2 cups flour, the baking soda, cinnamon, salt and nutmeg. In a large bowl, beat softened butter with a mixer on medium 30 seconds. Add granulated sugar; beat until light and fluffy. Beat in eggs and vanilla. Add flour mixture, beating until just combined. Stir in apples and coarsely chopped pecans
Line a 13×9-inch baking pan with parchment paper. Spread batter in prepared pan. Bake until golden and set in the center, 50 to 60 minutes.
Meanwhile, in a small bowl, stir together brown sugar, toasted pecans, melted butter, the remaining 2 tablespoons flour, the water and oats. Sprinkle over hot bars. Bake 5 minutes more.
Cool completely on wire rack. If desired, use parchment paper to lift bars out of pan. Place on a cutting board to cut into bars.